1. Field of the Invention
The present invention relates to a catalyst and its use in a catalytic cracking process. More particularly, the present invention relates to a cracking catalyst that minimizes coke production.
2. Description of Information Disclosures
Hydrocarbon cracking catalysts comprising a zeolite and discrete particles of alumina dispersed in an inorganic oxide matrix are known. See, for example, U.S. Pat. No. 4,283,309 and U.S. Pat. No. 4,259,212. Although the added alumina particles, which in themselves prior to being composited with the other components have relatively little cracking activity, the catalysts comprising the added alumina particles have increased activity, increased vanadium resistance, increased bottoms conversion and increased undesired coke production.
It has now been found that by treating the alumina particles with certain phosphorus compounds prior to compositing the alumina particles with the other catalysts or catalysts precursor components, the catalyst comprising the phosphorus-treated alumina particles has increased selectivity for naphtha components and produces less coke and gas. U.S. Pat. No. 4,454,241 discloses a phosphorus containing zeolitic catalyst made from a clay starting material. The catalyst is obtained by contacting a partially cation exchanged calcined zeolite-containing catalyst with a dihydrogen phosphate anion, e.g. ammonium hydrogen phosphate or dihydrogen phosphite anion.
U.S. Pat. No. 3,507,778 discloses a zeolite in combination with a phosphate promoted silica-magnesia catalyst for cracking petroleum fractions. Example 4 discloses an ammonium phosphate.
U.S. Pat. No. 4,228,036 discloses a cracking catalyst comprising an alumina-aluminum phosphate-silica matrix composited with a zeolite.
U.S. Pat. No. 4,179,358 discloses a cracking catalyst comprising a zeolite dispersed in a magnesia-alumina-aluminum phophate matrix.
U.S. Pat. No. 4,430,199 discloses passivation of contaminant metals on cracking catalysts by phosphorus addition. The phosphorus compound may be ammonium hydrogen phosphate. The phosphorus compound may be impregnated on an inert carrier such as calcined metakaolin clay that can be blended with the catalyst or added to the catalyst. See column 3, line 17 to 20 and column 10, lines 20 to 25.